/*
 * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package javax.sql.rowset.serial;

import java.sql.*;
import java.io.*;
import java.util.Arrays;

/**
 * A serialized mapping in the Java programming language of an SQL
 * <code>CLOB</code> value.
 * <P>
 * The <code>SerialClob</code> class provides a constructor for creating
 * an instance from a <code>Clob</code> object.  Note that the <code>Clob</code>
 * object should have brought the SQL <code>CLOB</code> value's data over
 * to the client before a <code>SerialClob</code> object
 * is constructed from it.  The data of an SQL <code>CLOB</code> value can
 * be materialized on the client as a stream of Unicode characters.
 * <P>
 * <code>SerialClob</code> methods make it possible to get a substring
 * from a <code>SerialClob</code> object or to locate the start of
 * a pattern of characters.
 *
 * <h3> Thread safety </h3>
 *
 * <p> A SerialClob is not safe for use by multiple concurrent threads.  If a
 * SerialClob is to be used by more than one thread then access to the SerialClob
 * should be controlled by appropriate synchronization.
 *
 * @author Jonathan Bruce
 */
public class SerialClob implements Clob, Serializable, Cloneable {

  /**
   * A serialized array of characters containing the data of the SQL
   * <code>CLOB</code> value that this <code>SerialClob</code> object
   * represents.
   *
   * @serial
   */
  private char buf[];

  /**
   * Internal Clob representation if SerialClob is initialized with a
   * Clob. Null if SerialClob is initialized with a char[].
   */
  private Clob clob;

  /**
   * The length in characters of this <code>SerialClob</code> object's
   * internal array of characters.
   *
   * @serial
   */
  private long len;

  /**
   * The original length in characters of this <code>SerialClob</code>
   * object's internal array of characters.
   *
   * @serial
   */
  private long origLen;

  /**
   * Constructs a <code>SerialClob</code> object that is a serialized version of
   * the given <code>char</code> array.
   * <p>
   * The new <code>SerialClob</code> object is initialized with the data from the
   * <code>char</code> array, thus allowing disconnected <code>RowSet</code>
   * objects to establish a serialized <code>Clob</code> object without touching
   * the data source.
   *
   * @param ch the char array representing the <code>Clob</code> object to be serialized
   * @throws SerialException if an error occurs during serialization
   * @throws SQLException if a SQL error occurs
   */
  public SerialClob(char ch[]) throws SerialException, SQLException {

    // %%% JMB. Agreed. Add code here to throw a SQLException if no
    // support is available for locatorsUpdateCopy=false
    // Serializing locators is not supported.

    len = ch.length;
    buf = new char[(int) len];
    for (int i = 0; i < len; i++) {
      buf[i] = ch[i];
    }
    origLen = len;
    clob = null;
  }

  /**
   * Constructs a <code>SerialClob</code> object that is a serialized
   * version of the given <code>Clob</code> object.
   * <P>
   * The new <code>SerialClob</code> object is initialized with the
   * data from the <code>Clob</code> object; therefore, the
   * <code>Clob</code> object should have previously brought the
   * SQL <code>CLOB</code> value's data over to the client from
   * the database. Otherwise, the new <code>SerialClob</code> object
   * object will contain no data.
   * <p>
   * Note: The <code>Clob</code> object supplied to this constructor must
   * return non-null for both the <code>Clob.getCharacterStream()</code>
   * and <code>Clob.getAsciiStream</code> methods. This <code>SerialClob</code>
   * constructor cannot serialize a <code>Clob</code> object in this instance
   * and will throw an <code>SQLException</code> object.
   *
   * @param clob the <code>Clob</code> object from which this <code>SerialClob</code> object is to
   * be constructed; cannot be null
   * @throws SerialException if an error occurs during serialization
   * @throws SQLException if a SQL error occurs in capturing the CLOB; if the <code>Clob</code>
   * object is a null; or if either of the <code>Clob.getCharacterStream()</code> and
   * <code>Clob.getAsciiStream()</code> methods on the <code>Clob</code> returns a null
   * @see java.sql.Clob
   */
  public SerialClob(Clob clob) throws SerialException, SQLException {

    if (clob == null) {
      throw new SQLException("Cannot instantiate a SerialClob " +
          "object with a null Clob object");
    }
    len = clob.length();
    this.clob = clob;
    buf = new char[(int) len];
    int read = 0;
    int offset = 0;

    try (Reader charStream = clob.getCharacterStream()) {
      if (charStream == null) {
        throw new SQLException("Invalid Clob object. The call to getCharacterStream " +
            "returned null which cannot be serialized.");
      }

      // Note: get an ASCII stream in order to null-check it,
      // even though we don't do anything with it.
      try (InputStream asciiStream = clob.getAsciiStream()) {
        if (asciiStream == null) {
          throw new SQLException("Invalid Clob object. The call to getAsciiStream " +
              "returned null which cannot be serialized.");
        }
      }

      try (Reader reader = new BufferedReader(charStream)) {
        do {
          read = reader.read(buf, offset, (int) (len - offset));
          offset += read;
        } while (read > 0);
      }
    } catch (java.io.IOException ex) {
      throw new SerialException("SerialClob: " + ex.getMessage());
    }

    origLen = len;
  }

  /**
   * Retrieves the number of characters in this <code>SerialClob</code>
   * object's array of characters.
   *
   * @return a <code>long</code> indicating the length in characters of this <code>SerialClob</code>
   * object's array of character
   * @throws SerialException if an error occurs; if {@code free} had previously been called on this
   * object
   */
  public long length() throws SerialException {
    isValid();
    return len;
  }

  /**
   * Returns this <code>SerialClob</code> object's data as a stream
   * of Unicode characters. Unlike the related method, <code>getAsciiStream</code>,
   * a stream is produced regardless of whether the <code>SerialClob</code> object
   * was created with a <code>Clob</code> object or a <code>char</code> array.
   *
   * @return a <code>java.io.Reader</code> object containing this <code>SerialClob</code> object's
   * data
   * @throws SerialException if an error occurs; if {@code free} had previously been called on this
   * object
   */
  public java.io.Reader getCharacterStream() throws SerialException {
    isValid();
    return (java.io.Reader) new CharArrayReader(buf);
  }

  /**
   * Retrieves the <code>CLOB</code> value designated by this <code>SerialClob</code>
   * object as an ascii stream. This method forwards the <code>getAsciiStream</code>
   * call to the underlying <code>Clob</code> object in the event that this
   * <code>SerialClob</code> object is instantiated with a <code>Clob</code>
   * object. If this <code>SerialClob</code> object is instantiated with
   * a <code>char</code> array, a <code>SerialException</code> object is thrown.
   *
   * @return a <code>java.io.InputStream</code> object containing this <code>SerialClob</code>
   * object's data
   * @throws SerialException if this {@code SerialClob} object was not instantiated with a
   * <code>Clob</code> object; if {@code free} had previously been called on this object
   * @throws SQLException if there is an error accessing the <code>CLOB</code> value represented by
   * the <code>Clob</code> object that was used to create this <code>SerialClob</code> object
   */
  public java.io.InputStream getAsciiStream() throws SerialException, SQLException {
    isValid();
    if (this.clob != null) {
      return this.clob.getAsciiStream();
    } else {
      throw new SerialException("Unsupported operation. SerialClob cannot " +
          "return a the CLOB value as an ascii stream, unless instantiated " +
          "with a fully implemented Clob object.");
    }
  }

  /**
   * Returns a copy of the substring contained in this
   * <code>SerialClob</code> object, starting at the given position
   * and continuing for the specified number or characters.
   *
   * @param pos the position of the first character in the substring to be copied; the first
   * character of the <code>SerialClob</code> object is at position <code>1</code>; must not be less
   * than <code>1</code>, and the sum of the starting position and the length of the substring must
   * be less than the length of this <code>SerialClob</code> object
   * @param length the number of characters in the substring to be returned; must not be greater
   * than the length of this <code>SerialClob</code> object, and the sum of the starting position
   * and the length of the substring must be less than the length of this <code>SerialClob</code>
   * object
   * @return a <code>String</code> object containing a substring of this <code>SerialClob</code>
   * object beginning at the given position and containing the specified number of consecutive
   * characters
   * @throws SerialException if either of the arguments is out of bounds; if {@code free} had
   * previously been called on this object
   */
  public String getSubString(long pos, int length) throws SerialException {

    isValid();
    if (pos < 1 || pos > this.length()) {
      throw new SerialException("Invalid position in SerialClob object set");
    }

    if ((pos - 1) + length > this.length()) {
      throw new SerialException("Invalid position and substring length");
    }

    try {
      return new String(buf, (int) pos - 1, length);

    } catch (StringIndexOutOfBoundsException e) {
      throw new SerialException("StringIndexOutOfBoundsException: " +
          e.getMessage());
    }

  }

  /**
   * Returns the position in this <code>SerialClob</code> object
   * where the given <code>String</code> object begins, starting
   * the search at the specified position. This method returns
   * <code>-1</code> if the pattern is not found.
   *
   * @param searchStr the <code>String</code> object for which to search
   * @param start the position in this <code>SerialClob</code> object at which to start the search;
   * the first position is <code>1</code>; must not be less than <code>1</code> nor greater than the
   * length of this <code>SerialClob</code> object
   * @return the position at which the given <code>String</code> object begins, starting the search
   * at the specified position; <code>-1</code> if the given <code>String</code> object is not found
   * or the starting position is out of bounds; position numbering for the return value starts at
   * <code>1</code>
   * @throws SerialException if the {@code free} method had been previously called on this object
   * @throws SQLException if there is an error accessing the Clob value from the database.
   */
  public long position(String searchStr, long start)
      throws SerialException, SQLException {
    isValid();
    if (start < 1 || start > len) {
      return -1;
    }

    char pattern[] = searchStr.toCharArray();

    int pos = (int) start - 1;
    int i = 0;
    long patlen = pattern.length;

    while (pos < len) {
      if (pattern[i] == buf[pos]) {
        if (i + 1 == patlen) {
          return (pos + 1) - (patlen - 1);
        }
        i++;
        pos++; // increment pos, and i

      } else if (pattern[i] != buf[pos]) {
        pos++; // increment pos only
      }
    }
    return -1; // not found
  }

  /**
   * Returns the position in this <code>SerialClob</code> object
   * where the given <code>Clob</code> signature begins, starting
   * the search at the specified position. This method returns
   * <code>-1</code> if the pattern is not found.
   *
   * @param searchStr the <code>Clob</code> object for which to search
   * @param start the position in this <code>SerialClob</code> object at which to begin the search;
   * the first position is <code>1</code>; must not be less than <code>1</code> nor greater than the
   * length of this <code>SerialClob</code> object
   * @return the position at which the given <code>Clob</code> object begins in this
   * <code>SerialClob</code> object, at or after the specified starting position
   * @throws SerialException if an error occurs locating the Clob signature; if the {@code free}
   * method had been previously called on this object
   * @throws SQLException if there is an error accessing the Clob value from the database
   */
  public long position(Clob searchStr, long start)
      throws SerialException, SQLException {
    isValid();
    return position(searchStr.getSubString(1, (int) searchStr.length()), start);
  }

  /**
   * Writes the given Java <code>String</code> to the <code>CLOB</code>
   * value that this <code>SerialClob</code> object represents, at the position
   * <code>pos</code>.
   *
   * @param pos the position at which to start writing to the <code>CLOB</code> value that this
   * <code>SerialClob</code> object represents; the first position is <code>1</code>; must not be
   * less than <code>1</code> nor greater than the length of this <code>SerialClob</code> object
   * @param str the string to be written to the <code>CLOB</code> value that this
   * <code>SerialClob</code> object represents
   * @return the number of characters written
   * @throws SerialException if there is an error accessing the <code>CLOB</code> value; if an
   * invalid position is set; if an invalid offset value is set; if number of bytes to be written is
   * greater than the <code>SerialClob</code> length; or the combined values of the length and
   * offset is greater than the Clob buffer; if the {@code free} method had been previously called
   * on this object
   */
  public int setString(long pos, String str) throws SerialException {
    return (setString(pos, str, 0, str.length()));
  }

  /**
   * Writes <code>len</code> characters of <code>str</code>, starting
   * at character <code>offset</code>, to the <code>CLOB</code> value
   * that this <code>Clob</code> represents.
   *
   * @param pos the position at which to start writing to the <code>CLOB</code> value that this
   * <code>SerialClob</code> object represents; the first position is <code>1</code>; must not be
   * less than <code>1</code> nor greater than the length of this <code>SerialClob</code> object
   * @param str the string to be written to the <code>CLOB</code> value that this <code>Clob</code>
   * object represents
   * @param offset the offset into <code>str</code> to start reading the characters to be written
   * @param length the number of characters to be written
   * @return the number of characters written
   * @throws SerialException if there is an error accessing the <code>CLOB</code> value; if an
   * invalid position is set; if an invalid offset value is set; if number of bytes to be written is
   * greater than the <code>SerialClob</code> length; or the combined values of the length and
   * offset is greater than the Clob buffer; if the {@code free} method had been previously called
   * on this object
   */
  public int setString(long pos, String str, int offset, int length)
      throws SerialException {
    isValid();
    String temp = str.substring(offset);
    char cPattern[] = temp.toCharArray();

    if (offset < 0 || offset > str.length()) {
      throw new SerialException("Invalid offset in byte array set");
    }

    if (pos < 1 || pos > this.length()) {
      throw new SerialException("Invalid position in Clob object set");
    }

    if ((long) (length) > origLen) {
      throw new SerialException("Buffer is not sufficient to hold the value");
    }

    if ((length + offset) > str.length()) {
      // need check to ensure length + offset !> bytes.length
      throw new SerialException("Invalid OffSet. Cannot have combined offset " +
          " and length that is greater that the Blob buffer");
    }

    int i = 0;
    pos--;  //values in the array are at position one less
    while (i < length || (offset + i + 1) < (str.length() - offset)) {
      this.buf[(int) pos + i] = cPattern[offset + i];
      i++;
    }
    return i;
  }

  /**
   * Retrieves a stream to be used to write Ascii characters to the
   * <code>CLOB</code> value that this <code>SerialClob</code> object represents,
   * starting at position <code>pos</code>. This method forwards the
   * <code>setAsciiStream()</code> call to the underlying <code>Clob</code> object in
   * the event that this <code>SerialClob</code> object is instantiated with a
   * <code>Clob</code> object. If this <code>SerialClob</code> object is instantiated
   * with a <code>char</code> array, a <code>SerialException</code> object is thrown.
   *
   * @param pos the position at which to start writing to the <code>CLOB</code> object
   * @return the stream to which ASCII encoded characters can be written
   * @throws SerialException if SerialClob is not instantiated with a Clob object; if the {@code
   * free} method had been previously called on this object
   * @throws SQLException if there is an error accessing the <code>CLOB</code> value
   * @see #getAsciiStream
   */
  public java.io.OutputStream setAsciiStream(long pos)
      throws SerialException, SQLException {
    isValid();
    if (this.clob != null) {
      return this.clob.setAsciiStream(pos);
    } else {
      throw new SerialException("Unsupported operation. SerialClob cannot " +
          "return a writable ascii stream\n unless instantiated with a Clob object " +
          "that has a setAsciiStream() implementation");
    }
  }

  /**
   * Retrieves a stream to be used to write a stream of Unicode characters
   * to the <code>CLOB</code> value that this <code>SerialClob</code> object
   * represents, at position <code>pos</code>. This method forwards the
   * <code>setCharacterStream()</code> call to the underlying <code>Clob</code>
   * object in the event that this <code>SerialClob</code> object is instantiated with a
   * <code>Clob</code> object. If this <code>SerialClob</code> object is instantiated with
   * a <code>char</code> array, a <code>SerialException</code> is thrown.
   *
   * @param pos the position at which to start writing to the <code>CLOB</code> value
   * @return a stream to which Unicode encoded characters can be written
   * @throws SerialException if the SerialClob is not instantiated with a Clob object; if the {@code
   * free} method had been previously called on this object
   * @throws SQLException if there is an error accessing the <code>CLOB</code> value
   * @see #getCharacterStream
   */
  public java.io.Writer setCharacterStream(long pos)
      throws SerialException, SQLException {
    isValid();
    if (this.clob != null) {
      return this.clob.setCharacterStream(pos);
    } else {
      throw new SerialException("Unsupported operation. SerialClob cannot " +
          "return a writable character stream\n unless instantiated with a Clob object " +
          "that has a setCharacterStream implementation");
    }
  }

  /**
   * Truncates the <code>CLOB</code> value that this <code>SerialClob</code>
   * object represents so that it has a length of <code>len</code>
   * characters.
   * <p>
   * Truncating a <code>SerialClob</code> object to length 0 has the effect of
   * clearing its contents.
   *
   * @param length the length, in bytes, to which the <code>CLOB</code> value should be truncated
   * @throws SerialException if there is an error accessing the <code>CLOB</code> value; if the
   * {@code free} method had been previously called on this object
   */
  public void truncate(long length) throws SerialException {
    isValid();
    if (length > len) {
      throw new SerialException
          ("Length more than what can be truncated");
    } else {
      len = length;
      // re-size the buffer

      if (len == 0) {
        buf = new char[]{};
      } else {
        buf = (this.getSubString(1, (int) len)).toCharArray();
      }
    }
  }


  /**
   * Returns a {@code Reader} object that contains a partial
   * {@code SerialClob} value, starting
   * with the character specified by pos, which is length characters in length.
   *
   * @param pos the offset to the first character of the partial value to be retrieved.  The first
   * character in the {@code SerialClob} is at position 1.
   * @param length the length in characters of the partial value to be retrieved.
   * @return {@code Reader} through which the partial {@code SerialClob} value can be read.
   * @throws SQLException if pos is less than 1 or if pos is greater than the number of characters
   * in the {@code SerialClob} or if pos + length is greater than the number of characters in the
   * {@code SerialClob};
   * @throws SerialException if the {@code free} method had been previously called on this object
   * @since 1.6
   */
  public Reader getCharacterStream(long pos, long length) throws SQLException {
    isValid();
    if (pos < 1 || pos > len) {
      throw new SerialException("Invalid position in Clob object set");
    }

    if ((pos - 1) + length > len) {
      throw new SerialException("Invalid position and substring length");
    }
    if (length <= 0) {
      throw new SerialException("Invalid length specified");
    }
    return new CharArrayReader(buf, (int) pos, (int) length);
  }

  /**
   * This method frees the {@code SeriableClob} object and releases the
   * resources that it holds.
   * The object is invalid once the {@code free} method is called.
   * <p>
   * If {@code free} is called multiple times, the subsequent
   * calls to {@code free} are treated as a no-op.
   * </P>
   *
   * @throws SQLException if an error occurs releasing the Clob's resources
   * @since 1.6
   */
  public void free() throws SQLException {
    if (buf != null) {
      buf = null;
      if (clob != null) {
        clob.free();
      }
      clob = null;
    }
  }

  /**
   * Compares this SerialClob to the specified object.  The result is {@code
   * true} if and only if the argument is not {@code null} and is a {@code
   * SerialClob} object that represents the same sequence of characters as this
   * object.
   *
   * @param obj The object to compare this {@code SerialClob} against
   * @return {@code true} if the given object represents a {@code SerialClob} equivalent to this
   * SerialClob, {@code false} otherwise
   */
  public boolean equals(Object obj) {
    if (this == obj) {
      return true;
    }
    if (obj instanceof SerialClob) {
      SerialClob sc = (SerialClob) obj;
      if (this.len == sc.len) {
        return Arrays.equals(buf, sc.buf);
      }
    }
    return false;
  }

  /**
   * Returns a hash code for this {@code SerialClob}.
   *
   * @return a hash code value for this object.
   */
  public int hashCode() {
    return ((31 + Arrays.hashCode(buf)) * 31 + (int) len) * 31 + (int) origLen;
  }

  /**
   * Returns a clone of this {@code SerialClob}. The copy will contain a
   * reference to a clone of the internal character array, not a reference
   * to the original internal character array of this {@code SerialClob} object.
   * The underlying {@code Clob} object will be set to null.
   *
   * @return a clone of this SerialClob
   */
  public Object clone() {
    try {
      SerialClob sc = (SerialClob) super.clone();
      sc.buf = (buf != null) ? Arrays.copyOf(buf, (int) len) : null;
      sc.clob = null;
      return sc;
    } catch (CloneNotSupportedException ex) {
      // this shouldn't happen, since we are Cloneable
      throw new InternalError();
    }
  }

  /**
   * readObject is called to restore the state of the SerialClob from
   * a stream.
   */
  private void readObject(ObjectInputStream s)
      throws IOException, ClassNotFoundException {

    ObjectInputStream.GetField fields = s.readFields();
    char[] tmp = (char[]) fields.get("buf", null);
    if (tmp == null) {
      throw new InvalidObjectException("buf is null and should not be!");
    }
    buf = tmp.clone();
    len = fields.get("len", 0L);
    if (buf.length != len) {
      throw new InvalidObjectException("buf is not the expected size");
    }
    origLen = fields.get("origLen", 0L);
    clob = (Clob) fields.get("clob", null);
  }

  /**
   * writeObject is called to save the state of the SerialClob
   * to a stream.
   */
  private void writeObject(ObjectOutputStream s)
      throws IOException, ClassNotFoundException {

    ObjectOutputStream.PutField fields = s.putFields();
    fields.put("buf", buf);
    fields.put("len", len);
    fields.put("origLen", origLen);
    // Note: this check to see if it is an instance of Serializable
    // is for backwards compatibiity
    fields.put("clob", clob instanceof Serializable ? clob : null);
    s.writeFields();
  }

  /**
   * Check to see if this object had previously had its {@code free} method
   * called
   */
  private void isValid() throws SerialException {
    if (buf == null) {
      throw new SerialException("Error: You cannot call a method on a "
          + "SerialClob instance once free() has been called.");
    }
  }

  /**
   * The identifier that assists in the serialization of this {@code SerialClob}
   * object.
   */
  static final long serialVersionUID = -1662519690087375313L;
}
